A couple things I do when I ride for a few days.
Pack "throw away" underwear and t shirts, it saves on packing and doing laundry.
Stop and have water often!!
MAke sure you have cloths for all weather. and dress in layers. It's easier to take a layer off to cool off than it is to "hope" you warm up when the sun comes up
Have raingear, oh did I mention to have raingear?
Take some time to enjoy the ride. I've done 1200 mile days and I've done 100 mile days. A buddy and I went from Mass to Cali and back during the summer before my freshman year of college (22 years ago
) and the best days riding were the days that we had no place to be, we stayed off the highways and met the locals, talked to strangers at gas stations and diners.
make sure that your bike can handle the ride- tires and brakes are in good shape, fluid changes. I don't know what you ride, but I carry spare plugs, a patch kit, and tools that I can repair minor problems on the road
BRING a camera. not just your camera phone, a real camera
Set up a UPS or Fed-ex account. send things home that you aren't going to use for the remainder of your ride, or if you buy souvenirs
I don't know what your time period is, or your sleeping plans are, if you're going to sleeping bag/tent/camp. I suggest a cheap hotel room every 4 or 5 nights. Even a crappy bed is better than a sleeping bag